Recuperator



June 5, 1928. I 1,672,864

J. LUNDBORG RECUPERATOR Fi 1 Filed July 16, 1925 2 Sheets-Sheet 1 INVENTOR ATTORNE'Y Patented June 5, 1928.

UNITED STATES 1,672,864 E ENT OFFICE. I

JOSEPH LUNDBORG, OF YORK, N. Y., ASSIGNOR TO SURFACE COMBUSTION COMPANY, or'NEwpYoRx, N. Y.,

A CORPORATION OF NEW YORK.

nncurnna'ron.

This invention relates to recuperators, and more particularly to an improved recuperator assembly for continuously preheating fractory ducts of fines extending horizontally or-vertically through the casing. These flues generally serve to conduct the hot products of combustion or other heating mediumthrough the recuperator, while air or other fluid to be heated is circulated around theoutside of'the flues and takes on preheat by indirect heatexchange with the hot gases.

One of the greatest obstacles to efficient heat transfer between the hot gas and the cold air in'this general class of recuperator assemblies is apparently due to the resistance to heat transfer offered by the substantially quiescentfilms of heating gas adhering to the inner walls of the fines through which the cores of hot gas are passed and also to the heat transfer resistance of the dead films of air which form and adhere tenaciously to the outer walls of these flues. The resistance of even oneof these films is in general greater than the total resistance to heat'transfer of the relatively much thicker nieml'n-ane or wall of the. tileseparating the hot gases from the cold air, because of the very low heat conductivity of any gas, and accordingly it is ob'vious that in recuperators of the general class above described,'and particularly those recuperators in which the tiles are assembled to form straight line paths or ducts, both for the hot air and cold gas, extending the whole length or breadth of the recuperator, the heat transfer resistance must be very large since it represents the sum of the combined resistances offered by the walls of the tiling and by the films of dead gas and air on both sides thereof.

Other disadvantages, one or more of which characterize most of the hollow tile recuperator assemblies in common use, are that (1) their assembly is apt to call for numerous forms of tiling, often of complicated design,

the invention contemplates a recuperator Application filed July 16, 1925. Serial No. 43,963.

which cannot be machine molded, with the result that they are expensive to install, operate and repair and also require some time and care in assembly and in tearing out and replacing broken or leaky tiles; (2) that the general class of oddly formed tiles employed in the assembly are apt to have walls of excessive thickness in some parts and thinness in others, and in almost every case there is a sacrifice of one or more of the elements of compactness, mechanical strength and/or maximum heat transfer effectiveness per unit area of heating surface.

The primary object of the present invention is to provide'an improved recuperator of the general class above described incorporating inits assembly the muchvto be desired features-of simplicity and compactness of design, relatively low installation and operating costs,-ease of assembly and repair, and mechanical strength, together with increased heat vtransfer effectiveness per unit area of heating surface.

\Vith this object in view one feature of assembly of hollow tiles of substantially uniform 'andsimple design, each tile having external grooves to form air passages around its outer periphery, the corners of the grooves and cores on each tile being rounded to give to the tile a maximum mechanical strength with a minimum thickness oflwall separating the heating-gas Et'romthe air to be heated. c a 7 Another feature of the invention contemplates assembling these hollow externally grooved tiles end to end and side by side in horizontal layers arranged one above the other in a recuperator, and staggering the vertical joints between tiles in alternate layers, thus forming with "the outer grooves of adjacent tiles ducts through which the air I rising through the recuperator is conducted in a zigzag path andis caused to impinge substantially at right angles against the thin outer heat transferring floors of numerous tiles as its direction of flow changes from horizontal to vertical and back to horizontal each time it traverses a distance'not'exceed-v ing the height of one layer oftiler Another feature of the invention contemplates equipping each of these tiles with a male and female joint at opposite ends in order to provide tight butt oints between tiles against the leakage and mixing of the loo hot and cold gases passing through the recuperator, and to more securely bind the assembly of tiles into a solid structure.

lVith these and other objects and features in view the invention consists in the improved recuperator hereinafter described and particularly defined in the claims.

The various features of the invention are illustrated in the accompanying drawings, in which Fig. 1 is a view in perspective of the pre ferred form of hollow tile employed in the recuperator assembly;

Fig. 2 is a similar perspective view of a modified form of tile used to break the joints in alternate layers extending vertically of the recuperator.

Fig, 3 is a perspective view of a short form of hollow tile used to break the length of the recuperator heating fines;

Fig. 4 is a vertical cross sectional view through a reeuperator embodying the improved tiles;

Fig. 5 is a vertical sectional view of the recuperator taken at right angles to Fig. 4 on the vertical plane 5-5;

Fig. 6 is a horizontal sectional view of the recuperator taken at rightangles to Fig. 4 onthe plane 6-6;

Fig. 7 is a horizontal sectional View of the recuperator taken at right angles to Fig. 4 on the plane 7-7. p

Referring to they drawings the standard form of tile employed in assembling the recuperator structure, illustrated at 10 in Fig. 1, is shown as having a hollow central core 12 and two rectangular grooves or channels 14 extending around its entire outer periphery. The number of these grooves or channels 14 is not necessarily restricted to twobut may be one, two or more. The cores 12 and the grooves 14 are preferably rectangular in form but have rounded corners 16 in order that the mechanical strength of the tile will be as great as possible while at the same time presenting a minimum wall thick ness between the hot gases passed through the core 12 and the air or other gas to be heated as it is passed through the closed flues formed by channels 14 of adjacent tiles in the assembled recuperator.

The block 18 shown in Fig. 2 of the draW- ings differs from the standard form of block 10 shown in Fig. 1, in that it has a smaller core 12 and the outside grooves or channels 14 extend on only three sides thereof, namely on one vertical and two horizontal sides.

The fourtlr vertical side of block 18 is a plane surface designed to lie flat against the inner surface of the outer wall or casing ofthe recuperator (see Fig. 4).

The simple tile block 20 illustrated in Fig.

f the drawing is employed in cases where it is desired to break the length of the r'ecu perator .flues. It is preferably of short length and when used is positioned at the ends of the assembled rows of tiling (see Fig. 6). For this reason block 20 has no grooves or channels cut into its outer walls.

Each of the three forms of tiling blocks illustrated in Figs. 1, 2 and 3 is equipped with .male and female joint members 21 at opposite ends thereof for the purpose of insuring against leakage of.air or heating gases through the joints-between abutting tiles in the assembled recuperator structure. The chief object of using the alternate form of blocks 18, illustrated in Fig. 2 of the drawings, is to break or stagger the joints running vertically through the recuperator assembly between tiles in alternate layers of the assembly by thus offsetting the tiles,

in alternate layers the grooves 14 in one row of tile which register with grooves 14 in the next row of tiles below or above form closed air flues which traverse the rec uperator in, a zigzag course and thus change the direction of flow of the streams of air rising through the recuperator from horizontal to vertical and back to horizontal for each row of tiles passed in their upward course through the recuperator, (see Fig.4). By thus stagger: ing the joints between tiles in alternate la'yers the heat transfer capacity of the recuperator is materially increased, for this construction makes it impossible for any core of cool air to pass through the recuperator without inpinging several times directly against the heat transferring walls of successive blocks in its upward course through the recuperator. i

In the assembled recuperator illustrated in Figs. 4, 5, 6 and 7 the entrance flue 22, through which hot products of combustion or other heating gas is introduced into the recuperator as from a furnace or gas pro; ducer (not shown) is shown as at the back and top of the recuperator opening into a chamber 23 which extends through the entirewidth thereof. From entrance chamber 23 the heating gases are carried through the entire length of the recu erator by horizontal flues 24, formed by tie cores of tiles 1O assembled end to end, into a return chamber 26 at the front of the recuperator which also extends the full breadth and. height thereof. Here the hot gases descend and return to the back of the recuperator through horizontal fiues 24 lower down in the assembly (see Fig. 5). Chamber 23 is partitioned off into one or fnore divisional chambers by tiling blocks 28, extending the full width of the re cuperator, so as to prevent gas entering the recuperator through inlet 22 from escaping to the stack without passing through the re- Inn cuperator flues 24'. After traversing the length of the r'ecuperator at least once in each direction throughflues 24 and after} giving up a substantial portion of waste heat .to the walls of the fines during such passage,

the relatively cooled waste combustion gases pass out of the recuperator through a flue 30 which is preferably connected with the furnace stack (not shown). The number of times that the heating gases are passed through the length of the recuperator before exhausting them to the stack may be increased or diminished by inserting one or more additional rows of partition tiles 28 in chamber 23 and similar tile partitions 31 in chamber 26 between the openings of adjacent flues 24. Thus in case lack of space makes it necessary to employ a short recuperator it will often be advantageous to increase the height of the recuperator and the number of flues 24 traversing the length thereof, and by inserting several additional rows of partition tiles 28 and '31;

to force the heating gases to pass back and forth several times throughout the length of the recuperator in order to effectively recover the excess heat which they carry before exhausting them into the atmosphere.

The air or other gas to-be heated enters the recuperator from the front and at the base through a flue 32 running lengthwise through the center and extending the entire length of the structure. A damper 34 mounted at the entrance of this air fiueis adjustable to regulate the amount of air admitted to the recuperator in-accordance with the requirements of the furnace, gas producer, or whatever type of heating device is used in conjunction with the recuperator.

; The air can be Carriedihrough the recuperator by means of natural draft or with the help of a blower. and forced draft. After entering through the flue 34 the cold air is divided into a number of small streams,

each of which enters one of the shortvertical flues 36 formed by the registering grooves 14 of adjacent tiles 10 in the assembly (see Fig. 14). After rising vertically past the first layer of tiling each of these small air streams impinges substantially at right angles against the bottom heating surface of a tile in the next layer and its direction of flow is thereby changed from vertical tohorizontal. This horizontal flow of the air continues for a distance equal to half the width of one tile when the course of the air.

is again changed to vertical and it is passed through another flue'36 until it impinges against another tile in the third layer. In this manner the airadmitted into the recuperator through flue 32 is forced to follow a zigzag path upwardly through the entire height of the recuperator until it enters a chamber 38 at the top thereof. The chamber 38 has a length equal to the length of the active heating section of the recuperator and a width equal to the width of the active heating section (see Figs. 4 and 5). During their upward pmage through the recuperator, as will be seen from Fig. 4, the air ducted to the heating furnace gas producer or othenplace of use. The front wall 42 of the recuperator is shown as equipped with openings 44 to allow for inspection and cleaning of the flues and brickwork. These openings 44 are closed during operation by a refractory plug 46.

From the above description it will be seen that the products of combustion or other heating gases admitted into the recuperator through entrance flue 22 follow a' number of undulating paths through flues 24 as they traverse the recuperator from end'to end while descending to the bottom and to stack offtake 30. Likewise the cold air entering the base of the recuperator through the fine 32 splits up into a plurality of small streams, each of which follows a zigzag path which may gradually extend sidewise of the recu-' perator while ascending toward the top thereof. The two systems of flues forinedj respectively by the cores of the tiling'blocks presented by their walls and accordingly the inner walls of the flues 24 for instance present'a relatively large heat absorbing.

each of the heating flues 24 has a large number of air flues 36, each carrying a small stream of air, surrounding it at frequent intervals throughout its length, a relatively large effective heat absorbing surface ispresented for the indirect transfer of heat from the hot gases to the air and the heat transfer thus obtained is further increased by the form. of tiling employed. Thus by using tiling having rounded corners on the cores and external grooves, a considerable reduction of the thickness of the tile walls separating the heating gas from the air being heated is obtained without sacrificing mechanical strength. The large number of air fiues, each of relatively small capacity, extending around the periphery of each of the heating gas flues present a heat transmitting surface very large in proportion to the total cross sectional area inclosed therein. Likewise the heating gas lines are- -section of the flue.

()ne of the greatest factors in increasing the heat transferring elliciency of the present recuperator is the staggered arrangen'ient of the tiling blocks in alternate layers running vertically so'thalt'the'air passing through the fines formed by the peripheral grooves of adjacent blocks is forced to follow a zigzag path through the'recuperator and to impinge directly against 'the heating surfaces of successive blocks each time the direction of its course through the recuperator is changed from vertical to horizontal. By thus forcing the air to impinge at right angles against the heating surfaces of several blocks during its rise through the recuperator the films of dead air normally adhering to the heating surface against which this air stream is impinging are broken down and at least partial y destroyed, with the result that the amount of heat which it is possible to transfer from the surface of the tile to the rising stream of air is" greatly increased over that normally transmitted when a non-conductant film of air insulates the heat transmitting surface of the tile from the stream of air passing therethrough.

By using a standard form of til ng blocks such as that illustrated in Fig. 1 the recuperator assembly forming the subject-- of the present invention may be built very easily and rapidly because since only one form of block is used in the body of the structure the blocks do not have to be assembled according to plan but are all suited for use at any point. in the assembly and can be rapidly put into place and joined end to end and side by side in-courses. Other courses can be rapidly laid on top of the first one so that the transverse channels on the bottom surface of the blocks last laid register .with

those in the upper surface of the first course and the channels on each side register with similar channels on adjacent blocks to form fines for the air, while the hollow cores of abutting blocks in adjacent rows form several parallel ducts extending lengthwise of the recuperator for the heating gas. By using blocks of the modified form 18 illustrated in Fig. 2 for constructing the fines adjacent the side walls in alternate courses the butt joints between tiles in consecutive courses are broken so as to offset them preferably half a block crosswise of the recuperator assembly. Thus the peripheral grooves at one end of a block in the upper course register with the peripheral grooves at th e opposite end of a block in the lower course to break the direction of flow of the air rising. through the recuperator in the closed ducts thus formed.

The flue systems thus formed in the present recuperator for the heating gas and for the gas to be heated possess in combination much greater heat tranferring elliciency per unit area of heating surface than it is possible to seen-re with the class of recuper ators now commonly used for similar purposes, and in addition the recuperator assembly is of simple and compact design, permits of quick and ready assembly or repair, and has a, relatively low installation and operating cost, particularly since the recuperator tiling employed in the assembly is of such uniform and simple design as to permit of its being turned out rapidly mechanical molding apparatus. Bythe use of rabbeted male and female joints'at the hi) abutting ends of the tiles the flue system of I the present recuperator can be made. gas-0" tight and the joints thus formed-will not break down under vibration and materially strengthen and bind the assembled blocks into a solid structure.

The capacity of the recuperator is largely determined by its width and lengthand by the number of fines of a given cross sectional area which are employed. Another great advantage in using a st'andard form of block is that the height, length and/or width of the recuperator can be readily increased or decreased by simply adding 'to or removing some blocks and offsetting the side-walls or end-walls of the casing sutficiently to permit such addition or removal. The capacity of a given recuperator may also be somewhat increased by inserting one or more additional partition blocks in the entrance flue for the heating gases and thereby forcing the hotgases to traverse the recupenatmfrom end to end a greater number of times. it is very easy to cut down the capacity of the recuperator by scaling upand cutting out some of the tines for air and for heating gas .or by removing one or more of the partition blocks in the heating gas entrance flue.

Ill)

Likewise In cases Where it becomes desirable the present recuperator construction permits passing air or other gas to be heated through the fines Elli-and passing hot gases through the zigzag ducts 36. \Vhere the use of the recuperator fines is thus reversed the heating gases would probably be admitted to the recuperator at the top through the flue 40 in chamber 38 and would exit from the recuperator through the fine 32, while the-, ai'r or other'gas to be heated would enter the recuperator through the flue 30 and would exit from the top of the recuperator through flue :22. As a general rule the best results would probably be obtained when passing the heating gases through the tines 24 and the gases to be heated upwardly around the outside of these flues in the ducts 36, according to the preferred arrangement of the apparatus illustrated in the drawing and described above. v

The invention having been described what is claimed as new is:

1. A rccuperator assembly comprising the coml'iination ot a plurality ofhollow refractory tiles having spaced" open channels extending transversely to the bores about the entire periphery thereof, said tiles being arranged end to end in rows and side by side in parallel courses in an outer casing to form with their interior bores a series or sinuous broken paths traversing the recuperator from end to end and to form with their exterior channels enclosed ducts extending in a zigza g direction through the rccuperator in planes lying at right angles to the planes of the parallel courses and tile bores.

2. A recuperator assembly comprising the combination of a plurality of hollow tiles having open rectangular grooves extending about their outer peripheryat right angles to the longitudinal axis of the bores, together with a number othollow tiles having similar grooves extending transversely for threequarters of the distance around the outer periphery thereof, all "of said tiles beingas- .semblcd end to end in rqws and side bv side'- in layers to form with their interior bores fines extending from one end to the other of the recuperatorand with their exterior grooves zigzag ducts traversing the recuperator in alternate directions at right angles to the flues. i

3. In a recuperator assembly the combination of a plurality of interiorl bored and exteriorly grooved tiling bloc s arranged end to end and side by side in parallel courses, the bores of blocks in each course registering to form parallel flues extending from end to end of the recuperator and the abutting end joints of blocks in consecutive courses being ofi'set crosswise of the recupc'ator a distance such that the exterior grooves of the adjacent blocks register to .form enclosed ducts extending around the tines, said ducts lIl combination forming aplurality of zigzag paths traversing the recupcrator in parallel angles to the planes 0 the fines formed by the bores of the tile blocks. 1 .7

4. In a recuperat-or assembly the combination of a plurality of' interiorly bored and exteriorly grooved tiling blocks arranged end to end and side by side in parallel courses, the bores of abutting blocks in each course registering to form parallel lines ex lanes lying at. right tending lengthwise of the recuperator, and

of parallel ducts extending in a zigzag path' crosswise of the recuperator, the ends of abutting blocks being rabbeted to form male and female joints for the greater strength and resistance to leakage of the assembled whole and the abutting end joints of blocks in consecutive courses being ofi'sct crosswise of the rccuperator;

In a recupe 'ator assemhlythe coinbination of a plurality of interiorly bored and exterior-1y grooved tiling blocks arranged end to end and side by sidein parallel course registering to form parallel fluesextending lengthwise of the recuperator, and" the exterior grooves of ad'acent blocks in each course registering to orm a plurality of parallel ducts extending in a zigzag path crosswise of the recuperatorrsaid boresand grooves having substantially rectangular j' cross sections with rounded corners, and the abutting cud. joints of blocks in consecutive courses being offset the width of' oneha-l f a block crosswise of the recuperatori 6. In a recuperator assembly the combi-f;

nation of a plurality of interiorly bored and v cxteri'orly grooved tiling blocks assembled end to end in rows and side by side in par? allel courses, the ends of each abutting pair of blocks being joined by interlocking male i. and female joints and the'joints between' blocks in adjacent rows being offset a dis tance such thatinthe assembled structure the exterior groovcs'ot adjacent blocks register to form a plurality of small ductsflsurirounding each block and traversing the recuperator in a'zigzag course at, right angles to ,the fines formed by the registering bores of abutting blocks.

7. recuperator assembly.eomprising 't] ow; combination of a plurality of "l1ollow ;ti-lcs w;

having spaced open channels extending at right angles to the bores about the entire periphery, thereof, said tiles beingarranged end to end 'in' rows and'side-byside in courses one above the other in an outer casing to form with their. interior bores a series of fiuestraversing the length of the.

recuperator horizontally, from end to' end and to form with their exterio ychannels enclosed ducts, extending in 'zigz'ag fhori;

zontal and vertical paths crosswise andnpwardlythroughout the. height of therecuperator, said horizontal'flues opening at each endof the-recuperator intoychambers,- and -'-said chambers having partitionstlierein for forcing the gas passing through the recuperator ,to follow through. I

In testimony whereof I aflix my signature.

1 JOSEPH LUNDBORG.

a sinuous path there- S0 courses, the bores of abutting blocks in each 

